JPH05165359A - Thermal fixing device - Google Patents

Abstract

PURPOSE:To shorten a warm-up time, to completely save power, and to surely energize a heating resistor layer. CONSTITUTION:A fixing roller 21 is constituted by forming a pressure sensitive conductive rubber layer 25 on the outer periphery of a metallic rotary shaft 24 which is used also as an internal electrode, forming the heating resistor layer 26 on the outer periphery of the pressure sensitive conductive rubber layer, forming an external electrode layer 27 on the outer periphery of the heating resistor layer, and forming a protective film layer 28 on the outer periphery of the external electrode layer; and a paper feeding roller 22 is arranged to be opposed to the fixing roller 21, and the rubber layer 25 is locally compressed when a recording paper 23 is fed while being held by rollers 21 and 22, and the compressed part gets in a conducted state. Thus, the layer 26 is energized and locally generates heat so as to perform thermal fixing to the recording paper 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device applied to an electrophotographic printer such as a laser printer.

[0002]

2. Description of the Related Art A laser printer, for example, charges the surface of a photosensitive drum, records information as a latent electrostatic image by scanning a laser beam, develops the latent electrostatic image with toner, and transfers the resulting toner image. It is transferred to the recording paper that is conveyed and supplied in the section. Then, the recording paper on which the toner image is transferred is passed through a thermal fixing device so that the toner on the recording paper is fused and fixed on the paper surface.

As a heat fixing device used in such an apparatus, the one shown in FIG. 5 is conventionally known. In this configuration, a fixing roller 2 having a tubular halogen lamp 1 arranged in the center and a paper feeding roller 3 are arranged to face each other, and the recording paper 4 is nipped and conveyed by the fixing roller 2 and the paper feeding roller 3 to heat the fixing roller 2. Thus, the recording paper 4 is heat-fixed.

However, in such a thermal fixing device, the entire fixing roller 2 must be heated by the halogen lamp 1, which requires a large amount of electric power for the halogen lamp 1 and consumes a large amount of power. It was In addition, it takes time for the temperature of the fixing roller 2 to rise to a temperature suitable for fixing after the power is turned on, and therefore the time required for warm-up becomes long, and the printer is required to start the first printing. There was a problem that it took a long time.

Therefore, the one shown in FIG. 6 is known as one which can solve such a problem. In this configuration, a cylindrical fixing roller 11 and a paper feeding roller 12 are arranged so as to face each other, and the fixing roller 11 is heated from the inner peripheral surface toward the outer peripheral surface to form the heating resistor layer
3, the conductor layer 14, and the release material layer 15. Then, the electrode roller 16 is provided on the inner peripheral surface of the fixing roller 11 at a position facing the paper feed roller 12, and when the sensor 18 detects the conveyance supply of the recording paper 17, the power supply unit 19 operates at a predetermined timing thereafter and the power supply unit 19 operates. Current from 19 is electrode roller 1
6 flows to the heating resistor layer 13, the conductor layer 14, and the paper feed roller 12, and as a result, only the heating resistor layer 13 of the fixing roller 11 where the electrode roller 16 and the paper feed roller 12 face each other generates heat. It is supposed to do.

By heating only a part of the heating resistor layer 13 in this way, the surface temperature of the fixing roller 11 at the portion facing the paper feed roller 12 reaches the temperature required for fixing in a short time and the power consumption is reduced. It can be reduced.

[0007]

However, in the structure shown in FIG. 6, since the electrode roller 16 is inscribed in the heating resistor layer 13, the contact between the electrode and the heating resistor layer is close to line contact. Therefore, contact may be insufficient, and current may not be sufficiently supplied to the heating resistor layer.

Therefore, the present invention is intended to provide a heat fixing device capable of sufficiently shortening the warm-up time and saving power, and more reliably energizing the heating resistor layer.

[0009]

According to the present invention, a heating resistor layer is formed on the outer circumference of a pressure-sensitive conductive rubber layer which is normally in an insulating state, and when pressed, only the pressed portion becomes conductive. A voltage is applied to the fixing roller, the paper feed roller arranged to face the fixing roller, and the heating resistor layer of the fixing roller at the portion facing the paper feed roller via the pressure-sensitive conductive rubber layer at that portion. The pressure-applying conductive rubber layer of the fixing roller at a portion facing the paper feed roller is pressed by the paper feed roller at least when the medium to be fixed is passed.

[0010]

In the present invention having such a structure, when the medium to be fixed passes through the facing portion of the fixing roller and the paper feed roller, the pressure sensitive conductive rubber layer of the fixing roller at that portion is pressed by the paper feed roller. It As a result, the pressure-sensitive conductive rubber layer at the pressed portion becomes conductive, and a voltage is applied to the heating resistor layer via the conducting portion by the voltage applying means, and the heating resistor layer is locally energized to generate local heat. To do. Due to this local heat generation, the fixing target medium passing therethrough is thermally fixed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 21 is a fixing roller, 22 is a paper feed roller, and these rollers 21 and 22 are arranged opposite to each other. The recording paper 23, which is the medium to be fixed, passes through the facing portions of the rollers 21 and 22 in the direction indicated by the arrow in the figure.

The fixing roller 21 is provided with a metallic rotary shaft 24 which also serves as an internal electrode in the center thereof, and a pressure-sensitive conductive rubber layer 25 is formed on the outer periphery of the rotary shaft 24. The heat generating resistor layer 26 is formed on the outer periphery, the outer electrode layer 27 is formed on the outer periphery of the heat generating resistor layer 26 by a vapor deposition method, and the protective film layer 28 is also formed on the outer periphery of the outer electrode layer 27 by a vapor deposition method. Is formed.

The pressure-sensitive conductive rubber layer 25 is made of a material in which a conductive filler is mixed in rubber which is an insulating material, and the conductive fillers are usually separated from each other to maintain a high resistance state, that is, an insulating state. However, when pressed, the conductive fillers in the parts come into contact with each other to be in a conductive state, and a digitizer (trade name) is known as a pressure-sensitive conductive rubber application product having such a property. As the heating resistor layer 26, for example, a varistor having a positive resistance temperature characteristic in which the resistance value increases as the temperature rises is used. The paper feed roller 22 has a heat resistant elastic layer 30 such as silicon rubber or fluororubber formed around a rotary shaft 29.

The fixing roller 21 and the paper feed roller 22
As shown in FIG. 2, a main body housing 31 is rotatably supported by insulating bearings 32 and 33, and a drive motor 35 is connected to one end of a rotary shaft 29 of the paper feed roller 22 via a gear 34. Has been done.

As shown in FIG. 3, a slider 36 is provided in contact with one end of the rotary shaft 24 of the fixing roller 21, and a part of the protective film layer 28 on the other end side is provided along the circumference. Notch, and the slider 37 is provided in contact with the notch,
The contacts 36 and 37 are connected to a power source 38 to form a voltage applying means.

The pressure-sensitive conductive rubber layer 25 and the heating resistor layer 26 of the fixing roller 21 may be integrally formed, or may be formed in a pipe shape and combined together.

In this embodiment having such a structure, for example, when the fixing roller 21 and the paper feed roller 22 face each other without the recording paper 23 interposed, the pressure-sensitive conductive rubber layer 25 is formed.
Is insufficiently compressed and the pressure-sensitive conductive rubber layer 25 maintains an insulating state, and when the recording paper 23 is interposed between the fixing roller 21 and the paper feed roller 22 as shown in FIG.
A large pressing force acts on the fixing roller 21 from the fixing roller 21. As a result, the pressure-sensitive conductive rubber layer 25 forms the internal electrode of the rotating shaft
The fixing roller 2 is compressed between the fixing roller 2 and the conductive state.
The contact state between 1 and the paper feed roller 22 is preset.

However, when the recording paper 23 is not fed, the pressure-sensitive conductive rubber layer 25 is insulative at all parts, so that the heating resistor layer 26 is not energized, and therefore the heating resistor layer 26 is not energized. There is no fever of 26.

When the recording paper 23 is fed in this state and the recording paper 23 is interposed between the fixing roller 21 and the paper feeding roller 22, a large pressing force acts on the fixing roller 21 from the paper feeding roller 22. As a result, the portion of the pressure-sensitive conductive rubber layer 25 that opposes the paper feed roller 22 and the rotary shaft 24 that forms the internal electrode is compressed, and the portion shown by the mesh in FIG. 4 becomes conductive.

Therefore, the rotary shaft 24 and the pressure-sensitive conductive rubber layer 25
Of the heat generating resistor layer 2 via the conductive portion of the electrode and the external electrode layer 27.
6, the power supply voltage is applied, and the heating resistor layer 26 at that portion is applied.
An electric current flows to generate heat. The heat energy generated at that time is efficiently transmitted to the recording paper 23 through the extremely thin external electrode layer 27 and the protective film layer 28.

Since the fixing roller 21 rotates together with the rotation of the paper feed roller 22, the conductive portion of the pressure-sensitive conductive rubber layer 25 and the heat generating portion of the heating resistor layer 26 are moved by the rotation of the fixing roller 21. In this way, the fixing surface of the recording paper 23 is heated and fixed as the recording paper passes, and the fixing is completed when the recording paper has finished passing.

As described above, the heat generated by the heat generating resistor layer 26 is generated only when the recording paper 23 passes, and moreover, the paper feed roller 22.
This is a local heat generation at a portion where the fixing roller 21 and the fixing roller 21 face each other. Therefore, the surface temperature of the fixing roller 21 at the portion facing the paper feed roller 22 reaches the temperature required for fixing in a short time, and the warm-up can be almost eliminated.
Moreover, it consumes less power and can save power.

Further, since the rotating shaft 24 constituting the internal electrode is provided on the heating resistor layer 26 via the pressure-sensitive conductive rubber layer 25, the pressure-sensitive conductive rubber layer 25 is electrically connected to the heating resistor layer 26. The energization is surely performed without the possibility of unstable contact.

In the above embodiment, the internal electrode is used as the rotary shaft of the fixing roller, but the present invention is not limited to this. The fixing roller is cylindrical and the innermost peripheral layer of the fixing roller is formed. A pair of electrode rollers are inscribed in the pressure-sensitive conductive rubber layer at a position facing the paper feed roller so as to be inscribed in the pressure-sensitive conductive rubber layer. The heating resistor layer may be energized to generate heat. Even in this case, each electrode roller comes into contact with the elastic pressure-sensitive conductive rubber layer, and each electrode roller conducts electricity to the heating resistor layer through the pressure-sensitive conductive rubber layer. It is possible to make more reliable contact as compared with the case where is directly contacted with the heating resistor layer.

[0026]

As described above in detail, according to the present invention, it is possible to sufficiently shorten the warm-up time and save the power consumption, and more surely energize the heating resistor layer. Can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of the present invention.

FIG. 2 is a front view of the embodiment.

FIG. 3 is a view showing a voltage applying means of the embodiment.

FIG. 4 is a partially enlarged view for explaining an energization operation of the same embodiment.

FIG. 5 is a diagram showing a conventional example.

FIG. 6 is a diagram showing another conventional example.

[Explanation of symbols]

21 ... Fixing roller, 22 ... Paper feeding roller, 23 ... Recording paper, 24 ... Rotating shaft (internal electrode), 25 ... Pressure-sensitive conductive rubber layer, 26 ... Heating resistor layer, 27 ... External electrodes, 36, 37
… Contacts, 38… power supply.

Claims (1)

[Claims] 1. A fixing roller having a heating resistor layer formed on the outer periphery of a pressure-sensitive conductive rubber layer which is normally in an insulating state and becomes conductive only when pressed. From a paper feed roller arranged to face each other, and a voltage applying means for applying a voltage to the heating resistor layer of the fixing roller at a portion facing the paper feed roller via the pressure-sensitive conductive rubber layer at that portion. The heat fixing device is characterized in that the pressure-sensitive conductive rubber layer of the fixing roller at a portion facing the paper feed roller is pressed by the paper feed roller at least when the medium to be fixed is passed.